Chromium-free hardfacing welding consumable

ABSTRACT

Compositions for Chromium-free hardfacing welding consumables are provided that include between approximately 0.3% and approximately 1.5% Carbon, between approximately 0.2% and approximately 2.5% Manganese, between approximately 0.3% and approximately 1.3% Silicon, between approximately 1.3% and approximately 5.5% Boron, between approximately 1.0% and approximately 4.0% Nickel, between approximately 1.0% and approximately 6.0% of at least one of Titanium and Niobium, and between approximately 0.1% and approximately 2.0% Tungsten and/or Molybdenum. Additional welding consumable compositions and weld deposit compositions are also provided to provide hardfacing materials with little or no Chromium content.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 12/909,738filed on Oct. 21, 2010. The disclosure of the above application isincorporated herein by reference.

FIELD

The present disclosure relates to alloy compositions for arc welding andmore particularly to compositions without Chromium for hardfacingapplications.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Hardfacing relates generally to techniques or methods of applying ahard, wear resistant alloy to the surface of a substrate, such as asofter metal, to reduce wear caused by abrasion, erosion, corrosion, andheat, among other operational or environmental conditions. A variety ofmethods are available to apply the wear resistant alloy to thesubstrate, among which includes welding, where a welding wire (alsoknown as a welding consumable) is deposited over the substrate surfaceto produce a weld deposit that is highly wear resistant. The weldingwire may include a solid wire, metal-cored wire or a flux-cored wire,wherein the metal-cored wire generally comprises a metal sheath filledwith a powdered metal alloy and the flux-cored wire generally comprisesa mixture of powdered metal and fluxing ingredients.

Many welding wires have compositions that include Chromium to improvewear resistance and hardness. However, during a hardfacing application,the Chromium in the welding wire can produce undesirable levels ofHexavalent Chromium, which can be harmful to end users. End users thatbreathe Hexavalent Chromium compounds over an extended period of timecan experience irritation and/or damage to the nose, throat, and lungs.Additionally, irritation and/or damage to the eyes and skin can occur ifHexavalent Chromium contact is in high concentrations for a prolongedperiod of time. Therefore, use of Chromium must be closely monitored inorder to limit the levels of Hexavalent Chromium that may result fromhard-facing operations.

SUMMARY

In one form, a Chromium-free hardfacing welding consumable is providedthat comprises, by percent mass, between approximately 0.3% andapproximately 1.5% Carbon, between approximately 0.2% and approximately2.5% Manganese, between approximately 0.3% and approximately 1.3%Silicon, between approximately 1.3% and approximately 5.5% Boron,between approximately 1.0% and approximately 4.0% Nickel, betweenapproximately 1.0% and approximately 6.0% of at least one of Titaniumand Niobium, and between approximately 0.1% and approximately 2.0%Tungsten.

In another form, a Chromium-free hardfacing welding consumable isprovided that comprises, by percent mass, between approximately 0.3% andapproximately 1.5% Carbon, between approximately 0.2% and approximately2.5% Manganese, between approximately 0.3% and approximately 1.3%Silicon, between approximately 1.3% and approximately 5.5% Boron,between approximately 1.0% and approximately 4.0% Nickel, betweenapproximately 1.0% and approximately 6.0% of at least one of Titaniumand Niobium, and between approximately 0.1% and approximately 2.0%Molybdenum.

In yet another form, a weld deposit composition is provided thatcomprises, by percent mass, between approximately 0.15% andapproximately 1.4% Carbon, between approximately 0.15% and approximately2.0% Manganese, between approximately 0.15% and approximately 1.0%Silicon, between approximately 0.8% and approximately 3.8% Nickel,between approximately 0.8% and 6.0% at least one of Titanium andNiobium, between approximately 0.8% and approximately 4.5% Boron andbetween approximately 0.1% and approximately 2.0% Tungsten and/orMolybdenum.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Generally, a Chromium-free welding consumable is provided that isparticularly suitable for producing hardfacing/hardsurfacing welddeposits, with wear resistance and hardness equal to or greater thanthat of standard Chromium containing hardfacing deposits. The consumablecontains no Chromium, thus reducing or eliminating the emission ofHexavalent Chromium during the welding process.

The welding consumable, or wire, is manufactured by forming a mild steelsheath into a tube and filling it with various alloy powders and drawingit to size. When welded, the sheath and alloy powders produce amartensitic weld deposit matrix with finely dispersed boron carbides aswell as titanium and/or niobium carbides and borides, in addition toMolybdenum and Tungsten carbides and borides.

The present disclosure, in one form, includes a metal-cored welding wirethat comprises, by percent mass, between approximately 0.3 andapproximately 1.5% Carbon, between approximately 0.2 and approximately2.5% Manganese, between approximately 0.3 and approximately 1.3%Silicon, between approximately 1.3 and approximately 5.5% Boron, betweenapproximately 1.0% and approximately 4.0% Nickel, between approximately1.0% and approximately 6.0% Titanium and/or Niobium, and Tungsten and/orMolybdenum between approximately 0.1 and approximately 2.0%.

In another form of the present disclosure, for which certain testing hasbeen conducted, a Chromium-free welding consumable and its weld depositcomposition are set forth below (by percent mass) in Table 1:

TABLE 1 C Mn Si Cr Ni Nb W Mo B Fe Cr Free 1.0 2.0 0.8 0.00 2.0 3.1 0.50.5 4.2 Bal Wire Composition Weld 0.8 1.8 0.6 0.01 1.9 3.0 0.4 0.4 3.8Bal Deposit Composition

As shown, there is no Chromium content in the welding consumable itself,and very low levels of Chromium result in the weld deposit. Therefore,during hardfacing operations, the levels of Hexavalent Chromium are wellbelow the OSHA (Occupational Safety & Health Administration) PermissibleExposure Limits for all industries. It should be understood that thesecompositions are merely exemplary and that slight variations of thepercentages to produce the desired result of little to no Chromium inthe weld deposit are to be construed as falling within the scope of thepresent disclosure.

Carbon (C) is an element that improves hardness and strength. Thepreferred amount of Carbon, in one form of the present disclosure,comprises, by percent mass, between approximately 0.3% and approximately1.5% in the welding consumable. In one form of a weld deposit, theamount of Carbon comprises, by percent mass, between approximately 0.15%and approximately 1.4%.

Manganese (Mn) is an element that improves the strength and hardness andacts as a deoxidizer, in which the deoxidizer also acts as a grainrefiner when fine oxides are not floated out of the metal. The preferredamount of Manganese, in one form of the present disclosure, by percentmass, between approximately 0.2% and approximately 2.5% in the weldingconsumable. In one form of a weld deposit, the amount of Manganesecomprises, by percent mass, between approximately 0.15% andapproximately 2.0%.

Silicon (Si) is an element that acts as a deoxidizer and also as a grainrefiner when fine oxides are not floated out of the metal. The preferredamount of Silicon, in one form of the present disclosure, is by percentmass, between approximately 0.3% and approximately 1.3% in the weldingconsumable. In one form of a weld deposit, the amount of Siliconcomprises, by percent mass, between approximately 0.15% andapproximately 1.0%.

Boron (B) is an element that provides a fine structure to the weldoverlay and to further enhance the hardness. Furthermore, Boron providesinterstitial hardening in the matrix, strengthens the grain boundariesby accommodating mismatches due to incident lattice angles ofneighboring grains with respect to the common grain boundary, and byitself or in combination with Carbon, form nucleation sites asintermetallics with Titanium and/or Niobium. The preferred amount ofBoron, in one form of the present disclosure, is by percent mass,between approximately 1.3% and approximately 5.5% in the weldingconsumable. In one form of a weld deposit, the amount of Boroncomprises, by percent mass, between approximately 0.8% and approximately4.5%.

Nickel (Ni) is an element that provides improved ductility, whichimproves resistance to impacts of the hardfacing overlay. The preferredamount of Nickel, in one form of the present disclosure, is by percentmass, between approximately 1.0% and approximately 4.0% in the weldingconsumable. In one form of a weld deposit, the amount of Nickelcomprises, by percent mass, between approximately 0.8% and approximately3.8%.

Titanium (Ti) acts as a grain refiner and as a deoxidizer and is also apart of the Titanium Carbide precipitates that improve wear resistanceof the weld overlay. Niobium (Nb) acts as a carbide former and is also apart of the Niobium Carbide precipitates that improve wear resistance ofthe weld overlay. The preferred amount of Titanium and/or Niobium, inone form of the present disclosure, is by percent mass, betweenapproximately 1.0% and approximately 6.0% in the welding consumable. Inone form of a weld deposit, the amount of Titanium and/or Niobiumcomprises, by percent mass, between approximately 0.8% and approximately6.0%.

Tungsten (W) and/or Molybdenum (Mo) are provided to improve hardness andcorrosion resistance. More specifically, Tungsten and/or Molybdenum arealloying elements that can be used in steels to modify the structure byproviding solid solution strengthening of the matrix. Tungsten alsocombines with Boron and Carbon to form borides and carbides, thusimproving the wear performance of the overlay. Molybdenum, in additionto providing matrix strengthening, also enhances the corrosionresistance of the overlay. The preferred amount of Tungsten and/orMolybdenum, in one form of the present disclosure, is by percent mass,between approximately 0.1% and approximately 2.0% in the weldingconsumable. In one form of a weld deposit, the amount of Tungsten and/orMolybdenum comprises, by percent mass, between approximately 0.1% andapproximately 2.0%.

The fine grain size of the matrix combined with small evenly dispersedcarbides and borides contributes to the weld deposit to improve wearresistance. Deoxidizers such manganese and silicon have been added,which also act as grain refiners when fine oxides are not floated out ofthe metal. The percent weight boron as well as Titanium and/or Niobiumhas been balanced with the carbon so that when the carbide is formed,the matrix is depleted of both carbon and the carbide forming element.The resulting small amount of carbon and the addition of Tungsten and/orMolybdenum in the matrix allow the weld deposit to retain its corrosionresistance, while the finely dispersed carbides and borides greatlyimprove the wear resistance.

Other forms of the present disclosure include consumables for theshielded metal arc and flux cored arc welding processes.

In general, the welding consumable of present disclosure willconsistently produce a Chromium-free weld deposit, or a weld depositwith very little Chromium, which has equal or better wear resistancewhen compared to typical Chromium carbide hardfacing welding consumablesthat contain 15 to 40% Chromium. Table 2 below compares hardness,Chromium content, and wear resistance of a single layer weld deposit ofthe consumable of the present disclosure to a typical Chromium carbideand martensitic consumable. The wear test was conducted per ASTM G-65procedure A using 6,000 revolutions. (Chromium content is the undilutedweld metal percent by weight).

TABLE 2 Percent Percent G-65 Chromium Hexavalent Cr Welding HardnessWear Loss Content of Content of Consumable (HRC) (grams) Electrode FumeWelding electrode 65 to 69 0.14-.15  0.0% <0.005 of present disclosureTypical Chromium 56 to 63 0.15-.19 15-40%  0.03-0.14 carbide TypicalMartensitic 55 to 60  1.30-1.70 5-16% 0.023

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the gist of the disclosure areintended to be within the scope of the disclosure. For example, the welddeposit according to the teachings of the present disclosure may beproduced from welding wire such as flux-core wires, metal-cored wires,or solid wires, while remaining within the scope of the disclosure. Suchvariations are not to be regarded as a departure from the spirit andscope of the disclosure.

What is claimed is:
 1. A weld deposit composition consisting of, bypercent mass: between 0.15% and 1.4% Carbon; between 0.15% and 2.0%Manganese; between 0.15% and 1.0% Silicon; between 0.8% and 3.8% Nickel;between 0.8% and 6.0% of at least one of Titanium and Niobium; between0.8% and 4.5% Boron; between 0.1% and 0.8% in an amount of Tungsten andMolybdenum, where both Tungsten and Molybdenum are present in the welddeposit composition; less than 0.1% Chromium; and the remainder beingIron to total 100%.
 2. The weld deposit composition according to claim1, wherein the Carbon is 0.8%.
 3. The weld deposit composition accordingto claim 1, wherein the Manganese is 1.8%.
 4. The weld depositcomposition according to claim 1, wherein the Silicon is 0.6%.
 5. Theweld deposit composition according to claim 1, wherein the Boron is3.8%.
 6. The weld deposit composition according to claim 1, wherein theNickel is 1.9%.
 7. The weld deposit composition according to claim 1,wherein the at least one of Titanium and Niobium is 3.0%.
 8. The welddeposit composition according to claim 1, wherein the Titanium is 3.0%.9. The weld deposit composition according to claim 1, wherein theNiobium is 3.0%.
 10. The weld deposit composition according to claim 1,wherein the Tungsten is 0.4%.
 11. The weld deposit composition accordingto claim 1, wherein the weld deposit composition has a martensiticmatrix.
 12. The weld deposit composition according to claim 11, whereinat least one of titanium and niobium carbides are dispersed within thematrix.
 13. The weld deposit composition according to claim 12, whereinthe Boron, Titanium and Niobium are balanced with the Carbon so thatcarbides are formed such that the matrix is depleted of the Carbon andcarbide forming elements.
 14. The weld deposit composition according toclaim 1, wherein the weld deposit composition comprises a hardness of 65to 69 HRC.
 15. A weld deposit composition consisting of, by percentmass: 0.8% Carbon; 1.8% Manganese; 0.6% Silicon; 1.9% Nickel; 3.0% of atleast one of Titanium and Niobium; 3.8% Boron; between 0.1% and 0.8% inan amount of Tungsten and Molybdenum, where both Tungsten and Molybdenumare present in the weld deposit composition; and the remainder beingIron to total 100%.
 16. The weld deposit composition according to claim15, wherein the Tungsten is 0.4%.
 17. The weld deposit compositionaccording to claim 15, wherein the Molybdenum is 0.4%.
 18. The welddeposit composition according to claim 15, wherein the Niobium is 3.0%.19. The weld deposit composition according to claim 1, wherein theCarbon ranges between 0.8% and 1.4%.
 20. The weld deposit compositionaccording to claim 1, wherein the Boron ranges between 3.8% and 4.5%.21. The weld deposit composition according to claim 1, wherein theCarbon ranges between 0.8% and 1.4% and the Boron ranges between 3.8%and 4.5%.